Compensating boom hoist cable system for a telescopic boom for cranes or the like



Oct. 20, 1970 R. JCHNSTON ET 3,534,867

COMPENSATING BOOM HOIST CABLE SYSTEM FOR. A TELESCOPIC BOOM FOR CRANESOR THE LIKE 3 Sheets-Sheet 1 Filed July 25. 1968 INVENTGRS:

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ATTORNEY Get. 20, 1970 JOHNSTON ET AL 3,534,867

COMPENSATING BOOM HOIST CABLE SYSTEM FOR A TELESCOPIC BOOM FOR CRANES ORTHE LIKE 5 Sheets-Sheet 2 Filed July 26, 1968 \NVENTOB5 Z0 GEE 4 Jo /v:701V 04 W0 6. 6H V55; 5

ATTORNEY Oct. 20, 1970 JOHNSTON ETAL 3,534,867

COMPENSATING BOOM HOIST CABLE SYSTEM FOR A TELESCOPIC BOOM FOR CRANES ORTHE LIKE SSheets-Sheet 3 Filed July 25, 1968 \NvEN'ro: EasseLJdmvsroMDAN/ID 6. 6/43 5545 United States Patent Oflice 3,534,867 Patented Oct.20, 1970 COMPENSATING BOOM HOIST CABLE SYSTEM FOR A TELESCOPIC BOOM FORCRANES OR THE LIKE Roger L. Johnston, Pewaukee, and David G. Ghysels,

Oconomowoc, Wis., assignors to Harnischfeger Corporation, Milwaukee,Wis., a corporation of Wisconsin Filed July 25, 1968, Ser. No. 747,673Int. Cl. B66c 23/04 US. Cl. 212-55 7 Claims ABSTRACT OF THE DISCLOSUREAn adjustable length boom having a boom hoist cable system extendingbetween the deck and the boom sections so that the outer end of the boomis supported from the deck and the boom sections are also individuallysupported.

BACKGROUND OF THE INVENTION A boom is supported in an angular positionby cables or the like extending from an anchor point on the deck supportstructure to the upper end of the boom. Thus the boom is prevented fromdeflecting under load and can be made without being excessively heavy.It is desirable to make these booms as light as possible for the loadsto be handled, not only from a standpoint of economy in manufacture, andease of transportation and handling, but also to increase their loadhandling capacity for any given boom size.

It is desirable to avoid manually changing the boom hoist cable systembetween the anchor point and the outer end of the boom when the boomlength is changed and it is desired to maintain the boom angle substantially constant. Prior art devices for accomplishing this have beenproposed and which use what are commonly referred to as automaticallycompensating cable systems. Such an arrangement is shown for a twosection boom in the US. Pat. 2,999,600 issued Sept. 12, 1961; that priorart system, however, cannot be used in a boom with more than twosections.

Another form of prior art, compensating pennant is shown in the US. Pat.2,819,803, issued Jan. 14, 1958, to Obenchain, where a single suspensioncable is utilized in a boom having more than two sections.

SUMMARY OF THE INVENTION The present invention provides an extensibleboom having three or more sections and an automatically compensatingboom hoist cable system between the anchor point and the outer end ofthe boom, and which also provides proper tension in the entire cablesystem. With the present invention, the outer end of the boom is alwayssupported from the anchor point, the boom angle can remain substantiallyconstant regardless of the amount of boom extension, and at the sametime the length and therefore tension of individual suspension cables toeach individual boom section can be individually set to provide propercable tension throughout the system. Thus the boom can be provided withthe precise amount of support required at any point along its length.Equal tension throughout the entire cable system can thus be providedand thereby prevent any weak link in the system.

More specifically, the entire compensating boom hoist cable systemincludes an individual suspension cable for each boom section, and eachcable can be made of such length so as to provide equal tensionthroughout the boom hoist cable system and also maintain substantialstraightness of the boom.

These and other objects and advantages will appear as this disclosureprogresses, reference being had to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view, more orless schematic in nature, of an extensible boom embodying the presentinvention, the boom being in its contracted position, and showing it asapplied to a truck crane;

FIG. 2 is a more or less schematic view of a portion of the FIG. 1 boom,but with the boom in a partially extended position, certain parts beingshown as broken away or removed for clarity in the drawing, the viewbeing enlarged from the FIG. 1 scale;

FIG. 3 is a more or less schematic, perspective view of the boom hoistcable system shown in FIGS. 1 and 2;

FIG. 4 is a view similar to FIG. 2, but showing the individualsuspension cables adjusted to a different position;

FIG. 5 is a view similar to FIG. 2 but showing the individual suspensioncables moved to diflerent individual positions relative to one another;

FIG. 6 is a view similar to FIG. l, but showing a modification of themanner in which the suspension cables are trained around the pulleymeans and anchored, and also showing a modified form of power means forextending one section.

DESCRIPTION OF A PREFERRED EMBODIMENT The boom B made in accordance withthe present invention can be used on various vehicles, loading docks orother stationary or movable supports, but it has been shown for purposesof illustrating the invention as being located on a revolving deck 1 ofa truck crane 2. The deck includes an upstanding, rigid part 3 and hasconventional power winches 4 and 5 mounted thereon.

The boom may be of three or more telescoping sections, and for purposesof illustrating the invention, a four section boom has been shown. Thesections are nested together and can be extended or contracted, beingsupported one within another by suitable rollers or the like (not shown)in the well known manner. When in use, the boom usually extends upwardlyfrom the deck at an angle to the perpendicular and often is of severalhundred feet in length when extended. In order for the boom toaccommodate maximum loads, particularly when the boom angle to theground is small, the boom should be as light in weight as possible, sothe boom weight itself does not limit the capacity of the boom,consistent of course with the required strength.

The load line 7 extends from winch 4 and over the boom point sheave 8 atthe outer end of the boom, and the load (not shown) is attached (forexample) to the hook 9 at the end of the load line 7 (FIG. 1).

The boom includes a base section 10 pivotally mounted for verticallyswinging on shaft 11 carried on the deck. The boom also includes anintermediate section 12 telescopingly slidable in section 10, a thirdsection 14 telescopingly slidable in section 12, and a fourth section 16which is telescopingly slidable in section 14 and extends outwardlytherefrom where the boom point sheave 8 is journalled.

Means are provided for telescopingly extending and contracting the boomsections. This means for causing extension or contracting of the boommay be of various types and is shown only briefly here in FIG. 1 as adouble acting hydraulic cylinder and piston means 20, or in FIG. 6 as achain and sprocket means 20a, connected between the base andintermediate sections for causing relative movement therebetween.Relative movement between the other sections 12 and 14, and 14 and 16 isaccomplished by flexible means 22 and 23, respectively, con.-

nected between sections 10, 12 and 14, and between sections 12, 14 and16. If a more complete description of the means for extending andcontracting the boom sections is deemed to be either necessary ordesirable, reference may be had to the copending US. application Ser.No. 747,672, filed July 25, 1968, and entitled, Flexible Means forPowering a Telescopic Boom in Extending and Contracting Directions.However, for purposes of this disclosure, this means, per se, may be ofany conventional and well known form, such as additional hydrauliccylinder and piston means, and further reference to it is not believednecessary or desirable.

In accordance with the present invention, a novel boom hoist cablesystem S is provided for supporting the adjustable length boom, and bymeans of which it is not necessary to manually adjust the cable systemwhen the length of the boom is to be changed and it is desired tomaintain approximately the same boom angle.

This automatically compensating boom hoist cable system S extendsgenerally between the anchor point on the deck, which point in effect isthe idler sheave 3a on the deck, and the outer end of the boom, as at25. With this system, the outer end of the boom is always supported fromthe anchor point, regardless of the length of the boom, and the boomangle can remain essentially constant.

The cable system includes boom lift line 29 and its reeving 29aconnected to winch 5 which is trained over idler sheave 3a and thenextended forwardly where it is fixed to a pulley means 30. Additionalpulley means 32 and 34 are provided and as all are similar, adescription of one will suffice. For purposes of illustrating theinvention, as shown clearly in FIG. 6, the pulley means have been shownas having a pair of pulleys journalled on the shaft. One such pulleymeans is provided for each boom section 10, 12 and are located generallyadjacent to but spaced upwardly from their respectiveboom section. Thus,a series of pulley means 30- 32 and 34 are provided, one respectively,for boom sections 10, 12 and 14.

The outermost section 16 commonly referred to as the boom tip, requiresno such pulley means.

Each boom section 10, 12 and 14 also have respective sheave means 40, 42and 44 journalled on and adjacent their outer or forward end. While theterm sheave has been used for purposes of describing the invention, theterm also includes pulleys, rollers, drums or the like. As shown in FIG.6, the sheave means for each section may comprise a pair of sheaves, onesheave on each end of a shaft which in turn is mounted on the end of thesection.

Individual suspension cables 50, 52 and 54 are provided, one for eachset of pulley means and sheave means 30, 40; 32, 42; and 34, 44,respectively.

The lift cable 29, the series of pulley means 30, 32 and 34, andportions of the cables 50, 52 and 54 together form a main boom hoistcable means CM which extends generally from the anchor point 3a to theboom tip 25 and at an acute angle to the boom B.

The suspension cables thus extend from the main cable means CM, onecable being connected to its respective boom section by being trainedaround its respective boom section sheave. Thus the suspension cablesact to individually support their respective boom section, as willappear. The tension in each cable can also be adjusted, as will appear,to equalize the tension throughout the cable system.

The suspension cables are anchored at their lower or rear ends to theadjoining telescopic boom section. For example, cables 50, 52 and 54 areanchored, respectively, adjacent the rear ends of boom sections 12, 14and 16, as at anchor points 12a, 14a and 16a.

The cables 50 and 52 are anchored at their other upper or forward ends,on the next pulley means outwardly along the boom, namely pulley means32 and 34, re

4 spectively. Cable 54 is anchored at its forward end to the boom tip,as at 25, in the FIGS. 15 device.

In the FIG. 6 arrangement, the cables 50, 52 and 54 are also trainedaround pulleys on the pulley means 32, 34 and 36, respectively, and thenextend rearwardly where they are anchored on the shafts of pulley means30, 32 and 34, respectively. Thus in the FIG. 6 arrangement, anadditional pulley means 36 is utilized on the outermost section 16. Anadditional mechanical advantage is obtained when the cables are anchoredas in FIG. 6.

Normally, the cables 50, 52 and 54 are of fixed length for any boomdesign or length, the cables providing additional reach for the cablemeans CM as the boom is extended, and vice versa.

The present cable system provides for individual adjustment of thetension in each suspension cable, and for individual and adjustablesupporting effect for the boom sections. Thus, variable loadingcharacteristics can be provided for the different boom sections fordifferent loading conditions. This adjustment is accomplished asfollows:

The length of the cables 50, 52 and 54 can be changed from that lengthshown in FIG. 1. When the cables are all shortened, for example, asshown in FIG. 4, the pulley means 30, 32 and 34 are more nearly directlyabove, that is more nearly in vertical alignment, with their respectivesheaves 40, 42 and 44. As a result, the cables are acting more nearly atright angles to their boom sections, and thereby provide a greaterlifting effect on or support for their respective sections.

When it is desired to vary the lifting effect between the differentcables, the pulley means may be moved individually with respect to oneanother and, if desired in opposite directions. For example, in FIG. 5,the pulley means 30 has been shifted rearwardly, or to the left of itssheave 40, by lengthening its pennant cable 50. On the other hand,pulley means 34 has been shifted forwardly, that is to the right of itssheave 44, by shortening its suspension cable 54. Consequently, cable 52has a greater lifting moment than cables or 54 because it is acting atmore of a right angle to the boom.

Thus the suspension cables can be changed in length for a particularcrane design, to thereby vary the distance between their pulley means,and consequently vary the amount of offset displacement between any onepulley means and its respective sheave on the adjacent boom section. Inthis manner, the supporting effect of a suspension cable on its boomsection can be selectively adusted.

What is claimed is:

1. In a crane, a mounting deck, an extensible and telescopic boomupstanding from the deck at an angle to the perpendicular, the boomhaving at least a base section, an inter-mediate section and a thirdsection mounted together for relative telescopic movement, said basesection being mounted on said deck, means for extending and contractingsaid boom sections, and a compensating boom hoist cable system of thetype wherein the boom angle remains substantially constant regardless ofthe amount of boom extension, said system including a main boom hoistcable means extending generally between said deck and the outer end ofthe boom at an acute angle to said boom, said system also including aseries of suspension cables extending from said main boom hoist cablemeans intermediate the length thereof and one suspension cable beingconnected to each boom section for individual support thereof.

2. The crane as defined in claim 1 further characterized in that saidboom hoist cable means includes a series of pulley means, one locatedgenerally adjacent to but spaced upwardly from each section; sheavemeans mounted on and adjacent the outer end of each section; and each ofsaid suspension cables extends from its respective pulley means and istrained over the respective sheave means on the adjacent boom sectionand is then anchored on the rearwardly adjoining telescoped section.

3. The crane defined in claim 2 further characterized in that saidsuspension cables each also extend from its said respective pulley meansover which it is trained and outwardly along the boom to the next pulleymeans for connection thereto, whereby an automatically compensating boomhoist cable system is formed.

4. The crane set forth in claim 3 further characterized in that saidsuspension cables can be changed in length to thereby vary the distancebetween said pulley means and consequently vary the amount of lateraldisplacement between any one pulley means and its respective sheavemeans on the adjacent boom section, whereby the supporting effect of asuspension cable on its boom section can be varied.

5. A crane of the type having a mounting deck, an ex tensible andtelescopic boom upstanding from the deck at an angle to theperpendicular, the boom having at least a base section, an intermediatesection and a third section mounted together for relative telescopicmovement, said base section being mounted on said deck, means forextending and contracting said boom sections, and a main boom hoistcable means extending generally between said deck and the outer end ofthe boom at an acute angle to said boom, the improvement comprising,said boom hoist cable means including a series of pulley means spacedtherealong, one pulley means being located generally adjacent to butspaced upwardly from each section; sheave means mounted on and adjacentthe outer end of each section; a series of suspension cables, onesuspension cable extending from each pulley means and trained over therespective sheave means on the adjacent boom section and then anchoredon the rearwardly adjoining telescoped section, to thereby provideindividual support for each boom section.

6. The crane defined in claim 5 further characterized in that some ofsaid suspension cables also extend from its said respective pulley meansover which it is trained and outwardly along the boom to the next pulleymeans for connection thereto, whereby an automatically compensating boomhoist cable system is formed.

7. The crane set forth in claim 6 further characterized in that saidsuspension cables can be changed in length to thereby vary the distancebetwen said pulley means and consequently vary the amount of lateraldisplacement between any one pulley means and its respective sheavemeans on the adjacent boom section, whereby the supporting effect of asuspension cable on its boom section can be varied.

References Cited UNITED STATES PATENTS 1,163,497 12/1915 Andersen 212551,345,304 6/1920 Fied 212 HARVEY C. HORNSBY, Primary Examiner US. Cl.X.R. 212-144

